Rockwell Automation 9301 Series RSView32 Users Guide - Manual (Page 79)

Setting up OPC and DDE communications
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3–17
Scanning for new tag values
When your RSView32 project is running, it must periodically update
its tag values in the value table.
For projects using OPC, values are updated by the OPC server at the
rate specified in the server product. The update rate you specify in the
Node editor is the requested data rate. The server uses this rate to
determine the fastest rate at which to notify your RSView32 project
(the OPC client) of tag value changes, if there are any changes. For
more details about setting the poll rate, see your server
documentation.
For projects using DDE, values are updated by the server at the rate
specified in the server product. When the server detects a change, it
provides the changed value to RSView32. For more details about
setting the poll rate, see your server documentation.
Scan class rates have no effect on DDE or OPC communications.
They affect only direct driver communications.